The human foot and ankle contain 26 bones and more than 100 muscles, tendons, and ligaments. This complex structure takes the brunt and impact of every step experienced by an individual. It is likely that the single largest source of complaint for foot ailments is related to heel pain.
One source of heel pain commonly observed is due to a condition known as recalcitrant plantar fasciitis. Plantar fasciitis occurs in the plantar fascia, a fibrous membrane disposed longitudinally across the bottom of the foot. The plantar fascia is attached at the heel bone (to the inner tubercle of the os calcis). The plantar fascia becomes broader and thinner as it extends longitudinally across the bottom of the foot, eventually dividing near the heads of the metatarsal bones into five processes, one for each of the five toes. The strongest ligament in the body, the plantar fascia's purpose is to protect the softer muscles and tissues of the bottom of the foot from injury, as well as to help maintain the integrity of the foot structure itself.
If the fascia becomes stretched or strained, the arch area becomes tender and swollen as well as the area about the heel bone. This inflammation is called plantar fasciitis and is typically painful from the heel throughout the arch up into the Achilles tendon. Patients suffering from this condition usually have relatively tight and inflexible heel cords, sometimes referred to as Achilles tendon tightness. When the heel cord is tight, it causes compensation in the foot with over pronation of the foot during weight bearing. The pain is consistently worse when you first get up in the morning and at the end of the day. The pain usually lurks in the heel pad and may include the arch ligament. A common tendency is to ignore the symptoms of the pain at first.
Plantar fasciitis is often caused by contracture of the Achilles tendon and the plantar fascia, which can occur at night during sleep, or during daytime inactivity. The Achilles tendon, the strongest and thickest tendon in the human body, begins at or about the middle of the posterior side of the leg extending downward towards the heel, narrowing as it progresses towards its point of insertion at the posterior surface of the os calcis. When an individual is standing, walking, running, or even sitting in a position in which the feet are in contact with the floor or other surface, both the plantar facia and the Achilles tendon are extended to varying degrees depending of course on the nature and intensity of the activity. During sleep, an individual has a natural tendency to plantarflex the ankle joint beyond the position which is normal during walking, standing, or sitting with one's feet on the floor. Plantarflexion is when the bottom of the foot is extended so as to form an angle with the lower leg of greater than 90°, i.e., extend such that the forefoot moves away from the body. Dorsiflexion is the opposite motion, when the foot is moved to a position in which the bottom of the foot forms an angle with the lower leg of less than 90°, i.e., such that the top of the foot moves toward the body.
Another condition, Achilles tendonitis can result from overuse of the tendon in sports activities, and can also result from a number of inflammatory diseases, of which rheumatoid arthritis is one.
As a result of plantar flexion during the night, the plantar facia and the Achilles tendon contract from their size and dimension normal to the walking, standing, or sitting positions. Upon arising, the plantar facia and the Achilles tendon are once again extended and stretched when the feet and ankles resume a normal position associated with walking or standing. Typically, it is when an individual arises following sleep or a period of extended recumbency that the effects of heel pain associated with plantar fasciitis, with, or without the associated Achilles tendon contracture, are observed, and in a significant number of cases the pain has been described as substantial.
For some time, a common method of treatment of plantar fasciitis and Achilles tendonitis has been the use of a night splint. The night splint typically consists, essentially, of a boot-like structure which is strapped to a patient's lower leg and foot, holding the foot relative to the lower leg in a position such that the ankle joint is held in slight dorsiflexion. In so doing, both the plantar fascia and the Achilles tendon are slightly extended and are not allowed to contract during the night. The use of night splints together with the variety of other elements of treatment including anti-inflammatory medications, physical therapy, and foot cushions for use during the daytime, has proved beneficial in the treatment of plantar fasciitis.
Various braces and splints, sometimes referred to as night splints, are advertised for treatment of plantar fasciitis and/or Achilles tendonitis. These devices typically consist of a molded splint or a combination of molded plastic and metal framework, with the dorsiflexion set at, for example, about 5°. Illustrative examples are disclosed in U.S. Pat. No. 5,399,155 (Strassburg et al.), U.S. Pat. No. 5,718,673 (Shipstead), U.S. Pat. No. 5,799,659 (Stano), U.S. Pat. No. 5,897,520 (Gerig), U.S. Pat. No. 6,019,741 (Prieskom), U.S. Pat. No. 6,267,742 (Krivosha et al.), U.S. Pat. No. 6,602,216 (Nordt, III), U.S. Pat. No. 6,695,797 (Trieloff), and U.S. Pat. No. 6,755,798 (McCarthy et al.), and U.S. Patent Application Publication Nos. 2004/0215123 (Slautterback et al.) and 2006/0064048 (Stano).
To treat plantar fasciitis or Achilles tendonitis, it is necessary to use considerable force to counteract the strong muscles and tendons of the lower leg and foot to maintain the affected foot and ankle in the desired dorsiflexion. If this force is applied improperly, pressure points can result, with resulting discomfort and complications for some patients. Some patients have reduced blood circulation or sensation in the feet, such as patients with diabetes, vascular insufficiency, polio, stroke, trauma, or neurological problems. In such patients, if they need to use a night splint for treatment of plantar fasciitis, it is important to minimize the pressure points exerted by the night splint on the patient's foot, while still exerting the necessary force on the foot and lower leg structure. The night splint must also not bruise or scratch the collateral leg during sleep, must not soil or tear bedding, and must be compatible with a sleeping partner.
The need exists for improved devices for treating plantar fasciitis and/or Achilles tendonitis.